The present invention relates to hand dishwashing composition designed and formulated to dissolve at a faster rate than previous composition of similar viscosity.
Liquid compositions are often designed to be used in diluted form. It is therefore necessary that the composition dissolves in water. In some cases, especially detergent compositions, the composition are thickened. Thickened compositions have several benefits, including: easier dispensing because they permit better control and accuracy of the dispensing process; improved dispersion of the composition over a surface; improved cling on non-horizontal surfaces. In addition to the technical reasons for using a thickened composition, consumers tend to equate composition thickness with richness and quality of cleaning performance.
Liquid compositions, especially thickened compositions can have the problem of poor mixing and dissolution in water. A composition that does not dissolve sufficiently quickly will give poorer cleaning and sudsing performance until the product has dissolved. This is not desirable, especially in the context of hand dishwashing where consumers rely on the appearance of suds to signal that the composition is active. In addition, poorly dissolving compositions do not rinse well from the hard surfaces such as dishware, especially glassware, leaving the surface feeling slippery or slimy. The consumer is therefore forced to use greater quantities of water to remove the residual composition from the surface.
Thickened hand dishwashing compositions are known in the prior art for example: Pril Gel sold by Henkel; Persil sold by Unilever; Palmolive Pots and Pans sold by Colgate and Palmolive, Power Max sold by Colgate and Palmolive. However these compositions dissolve more slowly and demonstrate the problems discussed above. It is an object of the present invention to provide a composition which dissolves in water at a faster rate that compositions described in the prior art having similar viscosity.
According to the present invention there is provided a composition suitable for use as a foaming hand dishwashing composition comprising a hydrophobic polymer having molecular weight of at least 500 and comprising alkylene oxide moieties, with the proviso that the composition does not comprise greater than 5% by weight of the composition of a builder.
The compositions of the present invention may be suitable for use in cleaning hard surfaces such as dishware including dishes, cups, cutlery, glassware, food storage containers, cutlery, cooking utensils, sinks and other kitchen surfaces. Dishwashing compositions are designed so as to foam, since consumers have been found to use the signal of foam as an indicator that the composition is active and ready to be used.
The cleaning composition, may be in any suitable form for example gel, paste or liquid. The cleaning composition may be in liquid form. Moreover the cleaning composition may be in liquid aqueous form. Where present water can be present at a level of from 30 to 80% by weight of the cleaning composition and/or from 40 to 70% and/or from 45 to 65%. The composition may have any suitable pH. In another embodiment, the pH of the composition can be adjusted to between 4 and 14. In even another embodiment, the composition can have a pH of between 7 and 13, and/or between 7 and 10. The pH of the composition can be adjusted using pH modifying ingredients known in the art.
The composition of the present invention may be thickened and can have a viscosity of greater than 300 and/or greater than 500 cps when measured at 20xc2x0 C. The present invention excludes compositions which are in the form of microemulsions.
Hydrophobic Polymer
The hydrophobic polymer of the present invention can be defined as a polymer having alkylene oxide moieties and an average molecular weight of at least 500 and/or at least 800. In one embodiment, the hydrophobic polymer has an average molecular weight of less than 10,000 and/or less than 5000 and/or less than 2000. In one embodiment, the hydrophobic polymer of the present invention can be defined as a polymer having alkylene oxide moieties and an average molecular weight of from 800 to 5000. In another embodiment, the hydrophobic polymer of the present invention can be defined as a polymer having alkylene oxide moieties and an average molecular weight of from 900 to 2000. In yet another embodiment, the hydrophobic polymer of the present invention can be defined as a polymer having alkylene oxide moieties and an average molecular weight of from 1000 to 1500. Nonlimiting examples of such hydrophobic polymers are polymeric glycols, which comprise alkylene oxide moieties, embodiments of which include, but are not limited to alkylene oxide moieties selected from ethylene oxide (EO), propylene oxide (PrO), butylene oxide (BO), pentylene oxide (PeO) and hexylene oxide (HO) moieties and mixtures thereof. However where ethylene oxide moieties are present they may be present in combination with another more hydrophobic moiety, for example propylene oxide or butylene oxide. In one embodiment, these hydrophobic polymers can be formed by adding blocks of alkylene oxide moieties to the ends of polypropylene glycol chains or other suitable alcohol. For example the polymer can be formed by reacting methanol with the alkylene oxide. In another embodiment, these hydrophobic polymers can be formed by reacting a mixture of alkylene oxide moieties with a suitable alcohol in a random fashion. Alternatively, these polymers can be made by polymerization of alkylene oxide groups, preferably PrO groups, or EO and PrO, or BO groups, with initiators that are commonly used for this reaction as known in the art.
In one embodiment, the polymeric glycol can be a polyproylene glycol. In one embodiment, the polypropylene glycol has an average molecular weight of at least 500 and/or from 500 to 10 000 and/or from 1000 and 5000 and/or from 1000 to 2500 and/or from 1500 to 2500. In another embodiment, the hydrophobic polymer can be a polybutylene glycol. In one embodiment, the polybutylene glycol has an average molecular weight of at least 500 and/or from 500 to 5000 and/or from 1000 to 4000 and/or from 1500 to 2500. In yet another embodiment, the hydrophobic polymer can be a polyhexylene glycol. In one embodiment, the polyhexylene glycol has an average molecular weight of at least 500 and/or from 800 to 5000 and/or from 1000 to 4000 and/or from 1500 to 2500.
The hydrophobic polymers of the present invention when incorporated into foaming liquid hand dishwashing compositions of the present invention prevent and/or reduce gelling and/or thickening of the liquid detergent compositions taught herein. Gelling has previously been observed in liquid detergent products prepared without the hydrophobic polymer as defined in the present invention, when the products are first contacted and diluted with water. Without being limited by theory, it is believed that this gelling phenomenon results from the surfactant system forming viscous surfactant phases (typically lamellar, spherulitic or hexagonal phases) at certain concentrations of surfactants and water. Alkylene oxide-containing compounds, especially butylenes oxide-containing compounds, have traditionally been used as non-foaming surfactants or suds suppressers. However the Applicants of the present invention have found that the polymers as described herein can be used in foaming hand dishwashing compositions to improve dissolution of the composition without significantly affecting the sudsing ability of the composition.
Without wishing to be bound by theory, it is believed that the hydrophobic polymers described above prevent the formation of the viscous surfactant phases formed upon dilution, because they can effectively interact with the ordered, structured layers of surfactant molecules, disrupt them and promote the formation of isotropic low-viscosity surfactant phases.
The hydrophobic polymers of the present invention may comprise on average at least 10% and/or at least 15% and/or at least 20% alkylene oxide moieties.
The hydrophobic polymer may be present in the composition at a level of from at least 0.05% and/or at least 0.1% and/or at least 0.2% by weight of the composition. The composition may also contain no more than 10% and/or no more than 8% and/or no more than 7% by weight of the composition of hydrophobic polymer.
Viscosity Test Method
The viscosity of the composition of the present invention is measured on a Brookfield viscometer model #LVDVII+ at 20xc2x0 C. The spindle used for these measurements is S31 with the appropriate speed to measure products of different viscosities; e.g., 12 rpm to measure products of viscosity greater than 1000 cps; 30 rpm to measure products with viscosities between 500 cps-1000 cps; 60 rpm to measure products with viscosities less than 500 cps.
Speed of Solubility
An internationally recognised test method for measuring solubility of a composition in water does not exist. The Applicants have thus developed a solubility test which takes into account the starting viscosity of the composition, the viscosity of the composition on dilution and the speed of dissolution in an agitation test known as the cylinder dissolution test. By measuring the difference in viscosity of the composition as is and on dilution we can first understand whether the composition increases or decreases in viscosity on dilution. In the situation where viscosity of the product increases on dilution, it is believed that surfactants present in the composition form the viscous surfactant phase which results in the composition becoming more viscose. Solubility is inversely related to viscosity, thus the greater the viscosity, the slower the solubilisation of the composition in water. Where viscosity of a composition decreases by a small amount only on dilution, it is believed that some of the surfactants may still be forming a viscous surfactant phase and thus some surfactants create the thickening effect, whilst others do not. This situation results in a composition which still does not dissolve adequately well. However, a composition that significantly decreases in viscosity on dilution is a composition that can be expected to dissolve well in water. Hence by measuring the increase or decrease in viscosity in water, we can understand the extent of solubilisation of the composition in water.
The cylinder dissolution test demonstrates the solubility of the composition in water by directly measuring how much agitation is required for the composition to dissolve. Dissolution of the composition is achieved when it can no longer be seen in the cylinder.
For this test, 0.6 mL of product, dyed dark blue for visibility, is squirted into a cylinder containing 500 mL of water at 35xc2x0 C. with a hardness of 15 g/gallon. The cylinder is then rotated through one full circle at 22 rpm. At the end of each successive rotation the cylinder is checked for remaining product. The cylinder is rotated until product is no longer visible. The number of rotations necessary for the product to have fully dissolved is noted. In a preferred embodiment of the present invention the compositions herein require no more than 8 rotations, more preferably no more than 7 rotations and most preferably no more than 5 rotations in order to dissolve fully.
Compositions were prepared according to the present invention and the initial viscosity (100% product), viscosity on dilution (80% product: 20% water and 60% product: 40% water) and solubility in water were measured. In addition the viscosity and solubility of hand dishwashing compositions currently sold on the market was also measured for comparison.